Drill with depth measurement system

ABSTRACT

A measurement system and method for determining a depth of penetration of a working portion of a surgical instrument (e.g., a rotating drill bit in a bore). A first sensor outputs a first signal representative of a displacement of the leading edge of the drill bit in the bore. A second sensor outputs a second signal representative of a force applied to the leading edge of the drill bit. A processor outputs a third signal representative of the depth of penetration of the leading edge of the drill bit when the leading edge of the drill bit passes from a first medium having a first density to a second medium having a second density. The third signal is based on the first and second signals.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/018,252 filed on Sep. 4, 2013 entitled “DRILL BIT PENETRATIONMEASUREMENT SYSTEMS AND METHODS”, the entirety of which is incorporatedby reference herein.

BACKGROUND

Inadequate and inaccurate depth measurement following orthopedicdrilling procedures may result in incorrect screw lengths, which canlead to surgical complications. Furthermore, determining the correctscrew length for a bore can be a time consuming procedure which isundesirable when tissue is exposed and potentially subjected toinfection.

As shown in FIGS. 1A and 1B, the bony structure of the human anatomyconsists mainly of cortical bone 10 having a hard outer cortex 12 and asoft inner medullary layer 14. Following traumatic injury, plate andscrew placement is critical for adequate repair of a fractured bone.Improper drilling lengths could lead to device instability, damage toanatomic structures, or device failure.

As shown in FIG. 1A, when using a rotating drill bit 16 to form abicortical bore 18 through the cortical bone 10, the rotating drill bit16 passes through a first portion 12 a of the hard outer cortex 12, asoft non-resistant medullary layer 14, and a second portion 12 b of thehard outer cortex 12.

As shown in FIG. 1B, when using a rotating drill bit 16 to form aunicortical bore 20 through the cortical bone 10, the rotating drill bit16 passes through an entry point 22 a of the hard outer cortex 12 and anexit point 22 b of the hard outer cortex 12 without penetrating the softnon-resistant medullary layer 14.

Previously proposed techniques for drilling and screw placement havebeen two-step processes, at best. For example, during an operation, abore is first drilled by a surgeon until the surgeon “feels” the drillbit pass completely through the bony structure. That is, the surgeonmust rely on his or her senses alone to determine when the drill bit haspassed completely through the bony structure. Once the surgeon believesthat he or she has passed completely through the structure, the drillbit is removed from the bore and a depth gage (not shown) is theninserted into the bore. The depth gage is grasped against the proximalend and a depth is recorded. A possible resulting complication of thisprocedure is that the surgeon may not precisely “feel” the drill bitpass through the second cortical layer, thereby possibly damaging tissueon the opposite side of the bone. Another complication may occur if thedepth gage is not properly inserted into the hole. If the gage isgrasped prior to passing the distal end of the bore, a size will bedetermined that is smaller than the true depth.

The process of drilling and depth measurement often requires more thanone attempt. Conservative drilling may result in incomplete drillingrequiring multiple passes. Furthermore, multiple depth measurements maybe required to confirm accurate placement of the gage. This processconsumes a substantial amount of surgical time resulting in a large costper patient. By combining the drilling and depth measurement processinto one accurate procedure, cost is reduced along with a decrease inpatient morbidity.

SUMMARY

The present disclosure relates generally to systems, methods, andapparatuses for use in connection with determining, with respect to areference point, a depth of penetration of an instrument working portion(e.g., a leading edge of a rotating drill bit in a bore) when theinstrument working portion (e.g., a leading edge of the drill bit) isadvanced (e.g., in the bore). More specifically, the present inventionrelates to a system and method for determining the length of either aunicortical or bicortical bore made in a bone of a patient withoutremoving the drill bit from the bore formed in the bone. Accordingly,the present disclosure may find application in the field of surgicaldrilling where the length of the bore made through a bone is to bedetermined to, for example, determine the appropriate size of hardwareto be used in connection with the bore that has been drilled.

Specifically, the present disclosure is related to embodiments of drillbit assemblies, drills, and/or drilling systems that may be specificallyadapted for use for drill bit penetration measurement. Accordingly, thedrill bit assemblies and drills disclosed herein may provide increasedefficiency, reliability, and accuracy in relation to a drill bitpenetration measurement system. For instance, in certain embodiments, adrill bit assembly may be used in conjunction with a drill as describedherein to provide an improved platform to facilitate measurement of abore created by the drill using a drill bit penetration measurementsystem without having to remove the drill bit from the bore duringoperation. However, it may be appreciated that the measurement systemsdescribed herein may be utilized with other surgical instruments suchas, for example, a surgical saw, a surgical grinder, of a surgicalchisel to determine a depth of penetration of a working portion of theinstrument relative to a reference point.

In this regard, systems for drill bit penetration measurement systemshave been proposed such as described in U.S. Pat. No. 6,665,948, theentirety of which is incorporated herein by reference. In this regard,the description presented herein may provide refinements and/oradditional features for use in connection with a drill bit penetrationmeasurement system. As such, the efficiency, accuracy, and or ergonomicsof drill bit penetration measurement systems may be improved.

Accordingly, a first aspect includes a drill bit assembly for use with adrill having a displacement sensor for outputting a signalrepresentative of a displacement of the drill bit with respect to areference point. The assembly includes a drill bit, a bushing, and anengagement member disposed on the bushing. The drill bit has a leadingedge disposed at a distal end of the drill bit and a shank disposedadjacent to a proximal end of the drill bit. The drill bit includes acylindrical member extending between the distal end and the shank. Theshank is adapted for engagement with a chuck of a drill, and thecylindrical member extends along an axis of rotation about which thecylindrical member rotates during drilling. The bushing includes anaperture sized to receive at least a portion of the cylindrical memberthrough the aperture. As such, the bushing is constrainedly moveablerelative to the cylindrical member in a direction along the axis ofrotation. The engagement member is adapted for engagement with adisplacement sensing arm of the displacement sensor. In this regard, theengagement member is engageable with the displacement sensing arm forcorresponding movement between the bushing and the displacement sensingarm.

A number of feature refinements and additional features are applicableto the first aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thefirst aspect.

For example, in an embodiment, the aperture of the bushing may define acylindrical opening extending from a distal end of the bushing to aproximal end of the bushing. In this case, the distal end of thecylindrical opening may comprise a reference surface. The referencesurface may extend at least partially circumferentially about the drillbit. In other embodiments, the bushing may be conformably shapedrelative to the cylindrical member to facilitate the constrainedmovement relative to the axis of rotation. In such embodiments, thebushing may or may not extend about entirety of the circumference of thecylindrical member. For example, the bushing may include a dished orconcave surface that is alignable with the cylindrical member forconstrained movement in a direction along the drilling axis.

In any regard, the bushing may be disposable adjacent the distal end ofthe bit. Accordingly, the reference surface may be alignable with theleading edge of the drill bit to define a reference point from whichdisplacement of the drill bit may be measured. In this regard, thedisplacement sensing arm to which the bushing is engageable may beoperatively engaged with a displacement sensor of a drill as will bedescribed in greater detail below. In this regard, the drill bit isrotatably advanceable into a bore such that the leading edge of thedrill bit is displaced relative to the reference surface upon therotatable advancement of the drill bit into the bore. Accordingly, whenthe engagement member operatively engages a displacement sensing arm ofa displacement sensor, the displacement sensor may measure thedisplacement of the leading edge from the reference surface.

In an embodiment, the reference surface may contact a peripheral portionextending about the bore upon rotational advancement of the drill bit tocreate the bore. The bushing may be maintainably engagable against theperipheral portion extending about the bore so as to maintain thereference point stationary against the peripheral portion of the bore ina direction along the axis of rotation. For instance, the bushing may bebiased toward the distal end of the drill bit (e.g., under the influenceof the displacement sensing arm or by another biasing member disposedrelative to the drill bit and bushing). In this regard, as the referencesurface of the bushing may be maintained adjacent to the surface to bedrilled, the accuracy of the displacement measure upon rotationaladvancement of the drill bit may be improved given the proximity ofcontact of the bushing defining the reference surface relative to thelocation of the bore.

In various embodiments, the engagement member may comprise anyappropriate mechanism for attachably connecting the bushing to adisplacement sensing arm. In one particular embodiment, the engagementmember may include a post extending from the bushing that is selectivelyengageable with the displacement sensing arm of the displacement sensor.In this regard, the post may facilitate relative rotational movementabout an axis of the post between the bushing and the displacementsensing arm (e.g., prior to engagement of the shank with a chuck of thedrill). This rotational movement may allow for improved ergonomics whenengaging the drill bit assembly with a drill by allowing the shank to bealigned with a chuck of a drill after engagement of the post with thedisplacement sensing arm.

In an embodiment, the drill bit assembly may be provided as a one-timeuse, disposable component for use in a surgery or other operation. Inthis regard, the drill bit assembly may include features that helpreduce the likelihood that the drill bit is reused in contradiction ofinstructions regarding one time use. Such features may at least reducethe functionality of the drill bit assembly (e.g., potentially to thepoint where the drill bit assembly is incapable of reuse). For example,in an embodiment, the shank may include a destructible portion that isat least partially destructible during a cleaning process. In oneparticular embodiment, the destructible portion may be meltable. In thisregard, a melting temperature of the destructible portion may be greaterthan an operating temperature of the drill bit and less than anautoclave temperature. As such, the destructible portion may remainintact during operation of the drill bit assembly. However, uponundergoing a cleaning or sterilization process (e.g., autoclaving), thedestructible portion may be at least partially degraded. In oneembodiment, the melting temperature of the destructible portion is notless than about 60° C. and not greater than about 110° C. Thedestructible portion may also be destroyed upon exposure to a cleaningor sanitizing chemical or the like used in the cleaning process (e.g.,as an alternative to or in addition to being meltable).

In view of the foregoing, the destruction of the destructible portionmay alter the shape of the shank of the drill bit such that engagementwith a drill may be at least partially prevented or degraded. Forinstance, the destructible portion may be used to at least partiallyestablish registration between the shank and a chuck to which the drillbit assembly is to be attached. Accordingly, upon destruction of thedestructible portion, registration between the drill bit assembly and achuck may be reduced (e.g., potentially to the point of inoperability ofthe drill bit). For example, the destructible portion may include aproximal end portion of the shank. In this regard, the destructibleportion may include at least a portion of an engagement feature forengagement of the shank by a chuck. In an embodiment, the destructibleportion may include at least a portion of at least one sidewall of theshank. Additionally or alternatively, the engagement feature may includea detent engageable by an engagement member in the chuck. As such, thedestructible portion, after having been exposed to a cleaning process,may not be registerable with respect to the chuck. That is, the surfacearea of the engagement feature of the shank in contact with the chuckmay be at least reduced upon exposure of the destructible portion to acleaning process.

A second aspect includes a method for use of a drill bit assembly with adrill having a displacement sensor for outputting a signalrepresentative of a displacement of a leading edge of the drill bitassembly with respect to a reference point. The method includes engaginga displacement sensing arm of the displacement sensor with an engagementmember of a bushing. The bushing is constrainedly moveable relative to adrill bit along an axis of rotation about which the drill bit rotatesduring drilling. The engaging may result in corresponding movement ofthe bushing and the displacement sensing arm. The method may includealigning a shank of the drill bit with a chuck member of the drill andsecuring the shank of the drill bit with the chuck of the drill torestrict axial movement between the drill bit and the chuck.

A number of feature refinements and additional features are applicableto the second aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thesecond aspect. For example, in an embodiment, the drill bit assembly maybe provided in accord with any of the features and/or featurerefinements described above in connection with the first aspect.

Additionally, in an embodiment, the method may include positioning adistal portion of the bushing adjacent to a leading edge of the drillbit at a distal portion thereof. In this regard, the method may alsoinclude contacting the leading edge of the drill bit to a surface of amedium to be drilled. Accordingly, the distal portion of the bushing maycontact the surface of the medium to be drilled. As such, the method mayalso include establishing the reference point when the leading edge ofthe drill bit and the distal portion of the bushing are in contact withthe surface of the medium to be drilled. The method may also includerotationally advancing the drill bit into the medium to be drilled, suchthat the leading edge advances in relation to the distal portion of thebushing in contact with the surface of the medium to be drilled. Thus,the method may include producing relative movement of the displacementsensing arm relative to the displacement sensor upon rotationallyadvancing the drill bit into the medium. As the displacement sensing armmay be operatively engaged with the displacement sensor, the method mayfurther include outputting a signal from the displacement sensorindicative of the amount of displacement of the leading edge of thedrill bit relative to the distal portion of the bushing.

A third aspect includes a drill bit for use in a medical drill forsingle use applications. The drill bit includes a leading edge, a shank,a cylindrical member, and a destructible portion. The leading edge isdisposed at a distal end of the drill bit. The shank is disposedadjacent to a proximal end of the drill bit, and the cylindrical memberextends along an axis of rotation between the distal end and theproximal end. The drill bit is rotatable about the axis of rotationduring drilling. Additionally, the shank comprises the destructibleportion that is at least partially destructible during a cleaningprocess.

A number of feature refinements and additional features are applicableto the third aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thethird aspect or any of the other aspects disclosed herein.

For example, in an embodiment, the destructible portion may be meltable.In this regard, a melting temperature of the destructible portion may begreater than an operating temperature of the drill bit and less than anautoclave temperature. For instance, the melting temperature of thedestructible portion may be not less than about 60° C. and not greaterthan about 110° C. Additionally, as referenced above in connection withthe first aspect, the destructible portion may be destroyed uponexposure to a cleaning or sanitizing chemical or the like used during acleaning and/or sanitizing process.

As described above with respect to the first aspect, the destructibleportion may comprise a proximal end portion of the shank. Thus, upondestruction of the destructible portion, at least a portion of the shankmay undergo a change in shape. Accordingly, the destructible portion mayinclude at least a portion of an engagement feature for engagement ofthe shank by a chuck. For instance, the destructible portion may includeat least a portion of at least one sidewall of the shank. Additionallyor alternatively, the engagement feature may include a detent engageableby the chuck (e.g., the detent features may correspond with aquick-change style chuck where the detents are used to selectivelyretain the shank in the chuck).

Accordingly, in an embodiment, the destructible portion, after havingbeen exposed to a cleaning process, may not be registerable with respectto the chuck. In this regard, the surface area of the sidewall of theshank may be at least reduced upon exposure of the destructible portionto a cleaning process (e.g., an autoclave process or a chemicalsanitation process).

A fourth aspect includes a method for a drill bit for use in a medicaldrill for single use applications. The method includes exposing thedrill bit to a cleaning process and degrading at least a portion of adestructible portion disposed on a shank of the drill bit in response tothe exposing. Additionally, a number of feature refinements andadditional features are applicable to the fourth aspect. These featurerefinements and additional features may be used individually or in anycombination. As such, each of the following features that will bediscussed may be, but are not required to be, used with any otherfeature or combination of features of any of the aspects discussedherein.

For instance, in an embodiment the exposing may include autoclaving thedrill bit. As such, the degrading may include melting at least a portionof the destructible portion in response to the autoclaving. The meltingmay occur at a temperature of not less than about 60° C. and not greaterthan about 110° C. In this regard, the destructible portion maywithstand temperatures associated with normal operation of the drillbit, but may be degraded (i.e., melted) upon exposure to the autoclavingprocess. In another embodiment, the exposing may include applying acleaning chemical to the drill bit such that the degrading comprisesremoval of at least a portion of the destructible portion in response toapplying the cleaning chemical.

In an embodiment, the degrading may result in changing a shape of ashank of the drill bit. Thus, the degrading may include removing atleast a portion of the destructible portion at a shank of the drill bit.The portion of the destructible portion removed may at least be aportion of an engagement feature for engagement of the shank by a chuck.For instance, the destructible portion may include at least a portion ofat least one sidewall of the shank or may include a detent engageable bythe chuck. In any regard, the degrading may result in reducing theregistration of the shank with respect to a chuck of a drill.

A fifth aspect includes a drill including a drill bit penetrationmeasuring system for determining, with respect to a reference point, adepth of penetration of a leading edge of a drill bit in a bore. Thedrill includes a chuck for engagement with a shank of a drill bit. Thechuck is operable to constrain a drill bit engaged by the chuck to limitrelative axial movement relative to an axis of rotation about which thedrill bit is rotated during drilling. The drill also includes adisplacement sensing arm extending from the drill that is engageablewith a bushing member that is constrainedly moveable with respect to(e.g., in a direction parallel to) the axis of rotation with respect toa drill bit engaged by the chuck. The drill also includes a displacementsensor disposed in a fixed relative position with respect to a drill bitengaged by the chuck at least in a direction corresponding to the axisof rotation. The displacement sensor is adapted for relative movementwith respect to the displacement sensing arm. Accordingly, thedisplacement sensor is operative to output a first signal representativeof the displacement of the drill sensing arm relative to thedisplacement sensor. The movement of the displacement sensing armrelative to the drill corresponds to displacement of the bushingrelative to a drill bit engaged by the chuck. In this regard, movementof the displacement sensing arm relative to the drill and thecorresponding movement of the drill bit relative to the bushing may bemeasured as an output of the displacement senor of the drill.

A number of feature refinements and additional features are applicableto the fifth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thefifth aspect. Furthermore, any of the features discussed in relation toany other aspect discussed herein may be used with the fifth aspect.

For example, in an embodiment, the displacement sensor may be disposedinternally to a drill housing and the displacement sensing arm mayextend from the drill housing. Accordingly, the displacement sensing armmay extend from the drill housing parallel to and offset from the axisof rotation. As such, at least a portion of the displacement sensing arm(e.g., a distal portion thereof) may extend towards a drill bit engagedby the chuck. As such, the displacement sensing arm may include a holeengageable with a post of the bushing to effectuate correspondingmovement of the displacement sensing arm and the bushing In anembodiment, the displacement sensor may include a linear variabledifferential displacement transducer (LVDT). Accordingly, a coil of theLVDT may be disposed in the housing and the displacement sensing arm mayinclude a moveable core displaceable with respect to the coil of theLVDT. The displacement sensor may have a total measureable travel of atleast about 2.5 inches (6.4 cm). Furthermore, the drill has a resolutionof at least about 0.002 inches (0.06 mm). However, any other appropriatetype of displacement sensor (e.g., a relative or absolute positionsensor) may be used such as, for example, an optical sensor or the like.

In an embodiment, the displacement sensing arm may be biased to a distalposition relative to a drill bit engaged by the chuck. Additionally oralternatively, the displacement sensing arm is selectively removablefrom the drill housing. Further still, the displacement sensing arm maybe selectively retainable in a proximal position. The displacementsensing arm may be selectively removable from a passage extendingthrough the drill housing, such that the passageway is selectivelyopened from a proximal end thereof to a distal end thereof (e.g., byremoval of the displacement sensing arm and/or removal of an end cap orthe like).

In an embodiment, the chuck of the drill may include a removableassembly engaged to a drive motor by way of a coupling receiver. Theremovable assembly may be attached to the drill by way of a releasemechanism. As such, the chuck may be selectively removable from thedrill.

In an embodiment, the drill may include a light emitter operable to emitlight in a direction toward the drill bit retained by the chuck.

A sixth aspect includes a method for use of a drill including a drillbit penetration measuring system for determining, with respect to areference point, a depth of penetration of leading edge of a drill bitin a bore. The method includes engaging a shank of a drill bit with achuck of the drill. The method also includes constraining the drill bitengaged by the chuck to limit axial movement relative to an axis ofrotation about which the drill bit is rotated during drilling. Themethod further includes connecting a displacement sensing arm extendingfrom the drill to a bushing member that is constrainedly moveable alongthe axis of rotation with respect to the drill bit engaged with thechuck.

A number of feature refinements and additional features are applicableto the sixth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of thesixth aspect. Furthermore, any of the features discussed in relation toany other aspect discussed herein may be used with the sixth aspect.

For example, the method may also include aligning a distal edge of thebushing with a leading edge of the drill bit and moving the displacementsensing arm relative to a displacement sensor of the drill. As such, themethod may include establishing the reference point upon alignment ofthe distal edge of the bushing with the leading edge of the drill bit.Furthermore, the method may include rotating the drill bit to rotatablyadvance the drill bit in a bore and detecting a relative movement of thedrill bit relative to the reference point by way of correspondingmovement of the displacement sensing arm relative to the displacementsensor. Further still, the method may include biasing the displacementsensing arm to a distal position, wherein the biasing maintains thedistal edge of the bushing in contact with a medium into which the drillbit is rotationally advanced.

A seventh aspect includes a drill comprising a drill bit penetrationmeasurement system for determining, with respect to a reference point, adepth of a penetration of a leading edge of a rotating drill bit in abore along an axis of rotation when the leading edge of the drill bitpasses from a first medium to a second medium, the first mediumcontiguous with the second medium, the first medium having a firstdensity, the second medium having a second density. The drill includes afirst sensor outputting a first signal representative of a displacement,with respect to the reference point, of the leading edge of the drillbit in the bore and a second sensor outputting a second signalrepresentative of a force applied to the leading edge of the drill bit.The drill also includes a chuck engageable with the drill bit.Accordingly, axial movement along the axis of rotation is constrainedbetween the chuck and the drill bit. The drill also includes a motorthat is operatively engaged with the chuck to rotate the drill bit. Themotor is constrained rotationally about the axis of rotation by asuspension member. However, the suspension member allows for movement ofthe motor linearly along the axis of rotation relative to the secondsensor. The drill also includes a processor in electrical communicationwith the first and second sensors. The processor is configured in afirst mode to output a third signal representative of the depth ofpenetration of the leading edge of the drill bit when the leading edgeof the drill bit passes from the first medium to the second medium. Thethird signal based on the first and second signals.

A number of feature refinements and additional features are applicableto the seventh aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of theseventh aspect. For example, any of the forgoing features described withrespect to any other aspect disclosed herein may be utilized with theseventh aspect.

Additionally, in an embodiment the first sensor may be a linear variabledifferential displacement transducer (LVDT). In an embodiment, thesecond sensor may be a load cell. The third signal may be output when asecond time derivative of the first signal is greater than zero and afirst time derivative of the second signal is less than zero.

In an embodiment, the first sensor may be a linear variable differentialdisplacement transducer (LVDT), the second signal may be a load cell,and the third signal may be output when the second time derivative ofthe first signal is greater than zero and a first time derivative of thesecond signal is less than zero. In an embodiment, the first medium maybe cortical bone surrounded by the second medium and the first mediummay enclose a third medium having a third density. In this regard, thesystem may include a mode selector and the processor may be configuredto operate in a mode selected from the group of modes consisting of thefirst mode wherein the third signal corresponds to a length of aunicortical drill path and a second mode, wherein the processor isconfigured such that the third signal corresponds to a length of abicortical drill path. In this regard, the first sensor may be a linearvariable differential displacement transducer, the second sensor may bea load sensor, and the processor, in the first mode, outputs the thirdsignal when a second time derivative of the first signal is greater thanzero and a first time derivative of the second signal is less than zero.Also, the processor, in the second mode, may output the third signal inresponse to a second occurrence of the second time derivative of thefirst signal being greater than zero and the first time derivative ofthe second signal being less than zero.

In an embodiment, the third signal may include an alert perceivable by auser of the drill. The alert may be an auditory alert. Additionally oralternatively, the alert may include a change in speed of the motor ofthe drill. For example, the alert may include stopping the rotation ofthe motor of the drill.

A eighth aspect includes a surgical instrument that includes aninstrument working portion adapted to engage a portion of a patient toperform a surgical operation. The surgical instrument also includes alight emitter adapted to emit light in a direction toward the patientwhen the instrument working portion is engaged with the portion of thepatient to perform the surgical operation.

A number of feature refinements and additional features are applicableto the eighth aspect. These feature refinements and additional featuresmay be used individually or in any combination. As such, each of thefollowing features that will be discussed may be, but are not requiredto be, used with any other feature or combination of features of theeighth aspect. For example, any of the forgoing features described withrespect to any or all of the foregoing aspects may be utilized with theeighth aspect.

For example, in an embodiment, the surgical instrument may correspond toany of the foregoing drill embodiments for determining a depth ofpenetration of a drill bit in a bore. However, in other embodiments, thesurgical instrument may comprise a surgical saw, a surgical grinder, asurgical chisel, or some other surgical instrument without limitation.

In an embodiment, the light emitter may include a light emitting diodelight source. For instance, in an embodiment, the light source may bedisposed within a housing of the surgical instrument. Alternatively, thelight source may be disposed remotely from the surgical instrument andtransmitted to the light emitter (e.g., by way of fiber optics or thelike).

In an embodiment, the surgical instrument may include a measurementsystem for determining, with respect to a reference point, a depth ofthe instrument working portion when the instrument working portionpasses from a first medium to a second medium. As such, any of theforegoing discussion with respect to embodiments of measurement systemsmay be provided in various embodiments without limitation. For instance,the surgical instrument may include a first sensor outputting a firstsignal representative of a displacement, with respect to the referencepoint, of the instrument working portion, a second sensor outputting asecond signal representative of a force applied to the instrumentworking portion, and a processor in electrical communication with thefirst and second sensors. The processor may be configured in a firstmode to output a third signal representative of the depth of penetrationof the instrument working portion of the surgical instrument when theinstrument working portion passes from the first medium to the secondmedium, the third signal based on the first and second signals.

In an embodiment, the light emitter may be selectively operable betweenan emitting state and a non-emitting state. For instance, the emittingstate may occur upon operation of the instrument working portion, andthe non-emitting state may occur upon cessation of operation of theinstrument working portion. Additionally or alternatively, the lightemitter may be selectively changed between the emitting state andnon-emitting state by way of a state switch or the like.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a sectional view of a bone illustrating a prior art method ofusing a drill mechanism to create a bicortical path through a corticalbone having multiple layers;

FIG. 1B is a sectional view of a bone illustrating a prior art method ofusing a drill mechanism to create a unicortical drill path through theouter layer of a cortical bone;

FIG. 2 is an elevation view, partially in cross section of an embodimentof a real-time, drill bit penetration measurement system;

FIG. 3A is an enlarged sectional view of the embodiment of the drill bitload measurement assembly of FIG. 2;

FIG. 3B is a sectional view of a portion of the drill bit loadmeasurement assembly taken along the line 3B-3B of FIG. 3A;

FIG. 4A is an enlarged sectional view of an embodiment of the drill bitload measurement assembly of FIG. 2;

FIG. 4B is a sectional view of a portion of the drill bit loadmeasurement assembly taken along the line 4B-4B of FIG. 4A;

FIG. 5 is an elevation view of an embodiment of a control panel of acontroller assembly of FIG. 2;

FIG. 6 is a schematic block diagram of the controller assembly of FIG. 2and the inputs and outputs of the controller assembly;

FIGS. 7A, 7B, and 7C are diagrams illustrating the position of the drillbit of FIG. 2 in bicortical bore of FIG. 1B and the corresponding outputof the first and second sensors of the displacement and load measurementassemblies of FIG. 2;

FIG. 8 is a flow diagram of an embodiment of a method for determiningthe depth of penetration of a drill bit;

FIG. 9 is a flow diagram of an embodiment method for determining thedepth of penetration of a drill bit;

FIGS. 10A-10C are perspective, side, and front views, respectively, ofan embodiment of a drill comprising a drill bit penetration measurementsystem;

FIG. 11 is a perspective view with a partial cutaway of a drill body ofan embodiment of a drill comprising a drill bit penetration measurementsystem;

FIG. 12 is a side view of a drill bit assembly for use with anembodiment of a drill comprising a drill bit penetration measurementsystem;

FIG. 13 is a perspective view of an embodiment of a drill bit with anintact destructible portion;

FIG. 14 is a perspective view of the embodiment of the drill bit of FIG.13, wherein the destructible portion has been at least partiallydestroyed;

FIG. 15 is a perspective view of an embodiment of a chuck for engagementof the bit of FIG. 13;

FIG. 16 is a perspective view in cross section of the embodiment of thechuck of FIG. 15;

FIG. 17 is a perspective view with a portion of the drill housing cutaway to show an embodiment of a coupling of a drill that corresponds tothe chuck of FIG. 15;

FIG. 18 is a perspective view of the proximal end of the chuck of FIG.15;

FIGS. 19A and 19B are cross sectional views of an embodiment of a drillcomprising a drill bit penetration measurement system;

FIGS. 20A-20D depict a progression for engagement of a drill bitassembly with a drill having a drill bit penetration measurement system;

FIG. 21A and 21B depict an embodiment of a controller for use inoperation of a drill having a drill bit penetration measurement system;

FIG. 22 is a cross sectional schematic view of a drill bit that has beenadvanced into a bore in a medium relative to a bushing engaged with adistal portion of a displacement sensing arm;

FIG. 23 is a perspective view of an embodiment of a drill with a portionof the drill housing cut away to show the interaction of a displacementsensing arm with the drill housing and an embodiment of a chuck release;and

FIGS. 24A-24C depict various embodiments of surgical instrumentsincluding light emitters.

DETAILED DESCRIPTION

Certain terminology is used in the following description for convenienceonly and is not limiting. The words “right,” “left”, “lower” and “upper”designate directions in the drawings to which reference is made. Thewords “inwardly” and “outwardly” refer to directions toward and awayfrom, respectively, the geometric center of the drill bit penetrationmeasurement system and designated parts thereof. The terminologyincludes the words above specifically mentioned, derivatives thereof andwords of similar import.

Additionally, as used in the claims and in the corresponding portion ofthe specification, the word “a” means “at least one”. Further, unlessotherwise defined the word “about” when used in conjunction with anumerical value means a range of values corresponding to the numericalvalue plus or minus ten percent of the numerical value. Still further,the word “or” has the meaning of a Boolean inclusive “Or”. For example,the phrase “A or B” means “A” alone or “B” alone or both “A” and “B”.

Referring to the drawings in detail, where like numerals indicate likeelements throughout there is shown in FIGS. 2-8 a first preferredembodiment of the drill bit penetration measurement system generallydesignated 100, and hereinafter referred to as the “measurement system”100, in accordance with the present invention. The measurement system100 is for determining, with respect to a reference point (not shown), adepth of penetration of the leading edge 16 a of a rotating drill bit 16in a bore when the leading edge 16 a of the drill bit 16 passes from afirst medium having a first density to a second medium adjacent thefirst medium and having a second density. The drill bit 16 is rotatablydriven by a drive 24 in a drill housing 26 of any typical well knownsurgical drill. In this regard and as may be appreciated below, ameasurement system 100 may be provided with an existing surgical drill(e.g., as a retrofit). In a further embodiment described in greaterdetail below, a measurement system 400 may be provided that is at leastpartially integrated into a drill 50 (e.g., as shown in FIGS. 10A-10C).

Preferably the first and second media are the hard outer cortex 12 and amedium such as air or other anatomical structure (not shown) surroundingthe outer surface of the cortical bone 10 and the bore is either thebicortical bore 18 or the unicortical bore 20 being drilled in thecortical bone 10. (See FIGS. 1A-1B). However, those skilled in the artwill understand from the present disclosure that the first and secondmedia can be the hard outer cortex 12 and the soft inner medullary layer14 of the cortical bone 10 or any adjacent media of different densitywithout departing from the scope of the invention. The artisan will alsounderstand that the reference point is a fixed point relative to whichthe displacement of the leading edge 16 a of the drill bit 16 ismeasured and may correspond to an initial position of the measurementsystem 100 or portion thereof as further discussed below.

Referring to FIGS. 2, 7A, 7B and 7C, the measurement system 100comprises a drill bit displacement measurement assembly 102, a drill bitload measurement assembly 104, and a controller assembly 106. Thedisplacement measurement assembly 102 is connected to the drill housing26. The connection can be made by a variety of well known mountingmethods such as a mount that clamps to the displacement measurementassembly 102 and is attached to the drill housing 26 by one or morethreaded fasteners. Alternative methods such as welding or adhesivebonding could also be used. The displacement measurement assembly 102has a first sensor 108 that outputs a first signal 108 s representativeof a displacement, with respect to the reference point, of the leadingedge 16 a of the drill bit 16 in the bore being drilled. Thedisplacement measurement assembly 102 preferably has an extension 110that is displaceable along a longitudinal axis. The extension 110 has adistal end 110 a that can be placed in registry with the reference pointwhen the leading edge 16 a of the drill bit 16 is positioned at theentry point, such as the entry point 18 a of the bicortical bore 18 orthe entry point 22 a of the unicortical bore 20 shown in FIGS. 1A-1B andmaintained in registry with the reference point throughout the drillingprocess. The reference point can be any anatomical structure proximal tothe desired location of the bore to be drilled. The extension 110 has aproximal end 110 b that is attached to the first sensor 102. Preferablythe sensor 102 is a linear variable differential displacement transducer(“LVDT”).

Referring to FIGS. 3A and 3B, the drill bit load measurement assembly104 comprises a housing 112, a thrust assembly 114 about which thehousing 112 is rotatable, a drill chuck 116 and a second sensor 118. Thehousing 112 has an axis of rotation 120 and is removably connected tothe drive 24 for rotation thereby. Preferably, the housing 112 has agenerally cylindrical-like shape and has a chamber 122 extending thelength thereof for containing a portion of the thrust assembly 114 and aportion of the drill chuck 116. Preferably, but not necessarily, thehousing 112 also has a proximal end 112 a with an outer diameter sizedfor being secured in a drive chuck 28 of the drive 24. Those skilled inthe art will understand from this disclosure that the drive chuck 28 canbe any well known surgical drill chuck through which surgicalinstruments are insertable.

The thrust assembly 114 is preferably a tube 124 with a bore 126therethrough. The bore 126 has a piston 128 moveable therein. The tube124 has a first portion 124 a having a first outer diameter and a secondportion 124 b having a second outer diameter less than the first outerdiameter. Similarly, the bore 126 has a first portion 126 a having afirst inner diameter and a second portion 126 b having a second innerdiameter less than the first inner diameter. Preferably, the piston 128is in the first portion 126 a of the bore 126. The second portion 124 bof the tube 114 extends beyond the proximal end 112 a of the housing112. The thrust assembly 114 is connected to the housing 112 by a firstbearing 130 and to the drill chuck 116 by a second bearing 132,preferably connected to the piston 128. Preferably, the first and secondbearings 130, 132 are thrust bearings suitable for use in a surgicalenvironment. Alternatively, the first and second bearings 130, 132 couldbe any device that permits the housing 112 and the drill chuck 116 torotate with respect to the thrust assembly 114 and allows a forceapplied to the leading edge 16 a of the drill bit 16 to be transferredto the thrust assembly 114. Preferably, but not necessarily, the thrustassembly 114 also is journaled with the housing 112 by a third bearing134.

The drill chuck 116 is connected to the housing 112 for rotationtherewith and to the thrust assembly 114 for rotation with respectthereto. The drill chuck 116 is moveable in translation along the axisof rotation 120 of the housing 112. Preferably, the drill chuck 116 is aconventional surgical drill chuck having a proximal end 116 a within thechamber 122 of the housing 112. The drill chuck is connected to thehousing 112 by a tab 136 extending radially outwardly from the proximalend 116 a of the drill chuck 116. The tab 136 extends into acorresponding slot 138 in the housing and is moveable therein intranslation along the axis of rotation 120 of the housing 112.Preferably, but not necessarily, the drill chuck 116 has diametricallyopposed tabs 136. Those of ordinary skill in the art will understandfrom the present disclosure that tabs 136 can be removably attached tothe drill chuck 116 by a threaded fastener (not shown) to facilitateinsertion of the proximal end 116 a of the drill chuck into the housing112. The proximal end 116 a of the drill chuck 116 additionally has aprojection 140 that extends into the bore 126 of the thrust assembly 114and is connected by the second bearing 132 to the piston of the thrustassembly 114.

The second sensor 118 in connected to the thrust assembly 114 andoutputs a second signal 118 s representative of a force applied to theleading edge 16 a of the drill bit 16. As shown in FIG. 3A, in onepreferred embodiment of the present invention, the second sensor 118 isa hydraulic pressure transducer and a portion of the bore 126 forms ahydraulic chamber 142 connecting the second sensor 118 with the piston128. As shown in FIG. 4A, in another preferred embodiment of the presentinvention, the second sensor 118′ is a load cell, such as apiezo-electric device, adjacent the piston 128 and a portion of the bore126 forms a conduit 142′ through which passes an electrical conductor144 connecting the piezo-electric device to the controller assembly 106.

Referring to FIGS. 2 and 5-6, the controller assembly 106 is inelectrical communication with the first sensor 108 and the second sensor118. In an embodiment, the controller assembly 106 has a controllerhousing 146 integral with the drill housing 26. However, with furtherreference to FIG. 21A, the controller housing 146 may also be providedas a remote unit. The controller assembly 1066 includes a processor 148in electrical communication with the first and second sensors 108, 118and with a mode selector 150 having a mode selector switch 154 and adisplay 152 having a reset button 153. The display 152, the reset button154 and the mode selector switch 154 may be mounted in a panel 156 ofthe controller housing 146. Alternatively, the display 152 or the resetbutton 153 or the mode selector 154 or any combination thereof could beseparately housed in the remote control unit that communicates with thefirst and second sensors 108, 118 by a wired or wireless link. Thedisplay 152 is for indicating the measured displacement of the leadingedge 16 a of the drill bit 16 to the user. The display 152 is controlledby the processor 148. The display 152 may continuously indicate thechanging displacement of the leading edge 16 a of the drill bit 16during the drilling of a bore and may also indicate the length of thebore at the when the drill bit 16 passes from one medium to another.

For instance, with continued reference to FIG. 21A and 21B, the display152 may be a touch sensitive display (e.g., a resistive or capacitivetype touch screen display). The display 152 may include an indication ofa bore diameter 160, the drill speed 162, a drill direction 164, and ascrew size indicator 166. The display 152 may also include patientinformation 168. The controller unit 106 may include a port 170 forengagement of a wired plug connection 172 with the drill 50. In thisregard, the drill 50 may be connected to the controller assembly 106 tosupply power to the drill 50 and communicate data between the drill 50and the controller assembly 106

Referring to FIGS. 1, 5-6, 7A, 7B, and 7C, the processor 148 isconfigured to operate in a first mode for drill bit penetrationmeasurement in unicortical bore drilling. In the first mode theprocessor 148 is configured to output a third signal 148 s ₁representative of the depth of penetration of the leading edge 16 a ofthe drill bit 16 when the leading edge 16 a of the drill bit 16 passesfrom the first medium to the second medium. The third signal 148 s ₁ isbased on the first and second signals 108 s, 118 s. Preferably, thethird signal 148 s ₁ is output upon a first occurrence 158 of a secondtime derivative of the first signal 108 s being greater than zero and afirst time derivative of the second signal 118 s being less than zero.In other words a positive acceleration of the drill bit 16 and aconcurrent reduction in the force applies to the leading edge 16 a ofthe drill bit 16 trigger the first occurrence 158. At the time of thefirst occurrence 158, the third signal 148 s ₁ corresponds to the lengthof the unicortical drill path.

Preferably, but not necessarily, the processor 148 is also configured tooperate in a second mode for drill bit penetration measurement inbicortical bore drilling and the mode selector 150 and mode selectorswitch 154 are for selecting between the first and second modes. Thesecond mode of operation is directed to the case where the first mediumis the cortical bone 12 surrounded by a second medium, such as the airor tissue surrounding the outer surface of the cortical bone 12, and thefirst medium encloses a third medium, such as the soft medullary layer14, having a third density. In the second mode, the processor 148 isconfigured to output the third signal 148 s ₂ in response to a secondoccurrence 160 of the second time derivative of the first signal 108 sbeing greater than zero and the first time derivative of the secondsignal 118 s being less than zero and corresponds to the length of thebicortical drill path. Accordingly, the third signal 148 s ₂ is outputafter the second time the drill bit 16 accelerates with a concurrentreduction in the force applied to the leading edge 16 a of the drill bit16.

Additionally or alternatively, the third signal 148 s (collectivelyreferring to 148 s ₁ and 148 s ₂ referenced above) may be at leastpartially based on additional parameters other than the first signal 108s and second signal 118 s. For instance, in at least some embodiments,the third signal 148 s may be at least partially based on a parameterassociated with the rotation of the drill bit 16. For instance, thespeed of the drive 24 turning the drill bit 16, the torque applied tothe drill bit 16 by the drive 24, or another appropriate parameterregarding the rotation of the bit 16 may be utilized in outputting thethird signal 148 s. Further still, parameters such as the diameter ofthe drill bit 16, the bone to be drilled, or other appropriateparameters may be utilized in determining the third signal 148 s.

Furthermore, the generation of the third signal 148 s may at leastpartially be customized based on the patient. In this regard,information regarding the patient may be provided to the controllerassembly 106 and utilized by the processor 148 in determining the thirdsignal 148 s. For instance, a patient's age, sex, and/or otherdemographic information may be provided. As may be appreciated, thedemographic data of the patient may provide a correlation to expectedbone density or other parameter regarding an expected property of thepatient's anatomy based on the demographic data of the patient. In thisregard, the demographic data may be used to correlate an expectedparameter associated with the patient's anatomy (e.g., bone density)that may be used as a factor in generation of the third signal 148 s. Inaddition, direct measurement of an anatomical parameter (e.g., bonedensity) for a given patient may be provided directly to the controllerassembly 106, thereby potentially eliminating the need to estimate theparameter based on demographic data.

Referring to FIG. 8, there is shown a block diagram of a first preferredmethod for determining, with respect to a reference point, the depth ofpenetration of the leading edge 16 a of a rotating drill bit 16 in abore when the leading edge 16 a of the drill bit 16 transitions from afirst medium having a first density, such as the hard outer cortex 12 ofa cortical bone 10, to a second adjacent medium having a second density,such air or tissue surrounding the outer surface of the cortical bone10. (FIG. 1B).

An initial position of the leading edge 16 a of the drill bit 16relative to the reference point is established (Step 205). The initialposition may be established by placing the leading edge 16 a of thedrill bit 16 against the outer surface of the cortical bone to bedrilled and by extending the distal end 10 a of the extension 110 of thedisplacement measurement assembly 102 to the reference point, such as ananatomical structure proximal to the desired location of the bore to bedrilled. As will be appreciated in the discussion of the embodimentsbelow, the reference point may also be established by a bushing memberof a drill bit assembly that is engaged with a displacement sensing armof a displacement sensor. With the leading edge 16 a of the drill bit 16and the measurement system reference point in the above positions (i.e.,aligned at a surface of the medium to be drilled), the measureddisplacement of the drill bit 16 is set to zero by pressing the resetbutton 153. Upon commencement of drilling, a first signal representingthe depth of penetration of the leading edge 16 a of the rotating drillbit 16 in the bore is output (Step 210). A second signal representing aforce applied to the leading edge of the drill bit is output (Step 215).A third signal based on the first and second signals and representativeof the depth of penetration of the leading edge of the drill bit whenthe leading edge of the drill bit passes from the first medium to thesecond medium is output (Step 220). Preferably, the third signal isoutput when the second time derivative of the first signal is greaterthan zero and a first time derivative of the second signal is less thanzero.

The third signal may be accompanied by (e.g., include) an alert that maybe perceivable by a user of the drill. As such, upon determination thatthe drill has passed through the bone (e.g., as described above), thealert may provide feedback to the user that the bone has been drilledthrough. As such, the alert may be an auditory alert such as a tone orthe like. In another embodiment, the alert may be a change in the speedof the motor of the drill. For instance, the drill may be slowed suchthat the user may be alerted to the fact that the drill has passedthrough the bone. Further still, the drill may be stopped at theoccurrence of the third signal. It may be appreciated that any otheruser perceivable alert may be provided including, for example, a visual,tactic, or other type of user perceivable feedback.

Referring to FIG. 9, there is shown a block diagram of a secondpreferred method for determining, with respect to a reference point, thedepth of a drilled unicortical bore 20 or a drilled bicortical bore 18.(FIGS. 1A and 1B). The mode selector switch 15 (MS) is set to the value“1” if a unicortical bore 20 is being drilled or set to the value “2” ifa bicortical bore 18 is being drilled (Step 305). An occurrence flag(OF) is set to zero (Step 310). An initial position of the leading edge16 a of the drill bit 16 relative to the reference point is established(Step 315), preferably in a manner similar to Step 205 discussed above.The displacement of the leading edge 16 a of the drill bit 16 and theforce applied to the leading edge 16 a of the drill bit 16 arecontinuously determined, (Steps 320 and 330, respectively). The secondtime derivative of the displacement of the leading edge 16 a of thedrill bit 16 (“drill bit acceleration”) is determined (Step 325) and thefirst time derivative of the force applied to the leading edge 16 a ofthe drill bit 16 (“change in applied force”) is determined (Step 335).The occurrence flag is updated by adding one to its present value (Step345) if the drill bit acceleration is positive and the change in appliedforce is negative (Step 340), otherwise determination of thedisplacement and the applied force continues. The depth of the bore isoutput (Step 355) if the value of the occurrence flag is equal to thevalue of the mode selector (Step 350), otherwise determination of thedisplacement and the applied force continues.

The components used to construct the present invention may consist of avariety of materials that are customarily used in the manufacture ofsurgical drills. One having ordinary skill in the art will readilyappreciate the materials that most desirably may be used to constructthe present invention. In a preferred embodiment, however, the drillingmechanism, drill bit displacement measurement assembly, the drill bitload measurement assembly and the structural elements of the controllerassembly may be constructed of a combination of polymeric materials(e.g., high strength plastic), polymers and stainless steel.

Furthermore, it may be appreciated that the spacing of the extension 110of the displacement sensor 102 from the drill bit 16 may introduce thepotential for errors or other disadvantages in determining thedisplacement of the drill bit 16 relative to the reference point. Forinstance, as the extension 110 may contact a structure that is offsetfrom the contact point between the leading edge 16 a of the drill bit 16and the medium to be drilled. Accordingly, any movement between thestructure contacted by the extension 110 and the medium to be drilledmay be falsely registered as relative movement of the drill 16 withrespect to the reference point. Furthermore, there may not be a rigidstructure to contact adjacent to the medium to be drilled, leading todisplacement of the structure contacted by the extension 110 (e.g., suchas in the case where the extension 110 may contact soft tissue adjacentto the medium to be drilled given the offset from the location to bedrilled). Furthermore, the offset nature of the extension 110 relativeto the contact between the drill bit 16 and the medium to be drilled maylead to other complications such as having to expose a greater surfaceof the medium to be drilled, which may adversely affect patientoutcomes.

As such, an improved embodiment of a drill with an improved displacementsensor including a displacement sensing arm that extends from the drillmay be provided. For example, such a displacement sensing arm may beprovided that may coordinate with a bushing member of a drill bitassembly that may be used with the drill. In this regard, the bushingmay move along the drill bit in a direction corresponding to the axis ofrotation of the drill bit. Upon engagement of the bushing and thedisplacement sensing arm, the bushing and displacement sensing arm mayundergo corresponding movement. As such, the bushing may be disposed incontact with the medium to be drilled when the leading edge of the drillbit is in contact with the medium. As such, a reference point may beestablished when the bushing and leading edge of the drill bit are bothin contact with the medium to be drilled. As the bushing is locatedadjacent to (e.g., partially or fully surrounding the drill bit), thebushing may facilitate contact with the medium at or very near thelocation to be drilled prior to creating a bore as described above. Inthis regard, the reference point may be more accurately maintained asthe bushing may contact at least a portion of a periphery of the borecreated in the medium drilled. That is, the bushing may remain inintimate contact with the medium to be drilled adjacent to the borecreated. This may prevent false displacement readings attributable tothe foregoing problems associated with an offset extension 110.Furthermore, the amount of contact of the drill may be localized at thelocation to be drilled, thus allowing for potentially less intrusionwhen performing drilling operations.

For example, with additional reference to FIGS. 10A-10C and 11, anembodiment of a drill 50 comprising an embodiment of a measurementsystem 400 is shown. The drill 50 may be adapted for use with a drillbit assembly 60 (shown in FIG. 12) that may include a bushing 452. Thedrill 50 may integrally comprise at least some components of themeasurement system 400 to facilitate operation of the measurement system400 in connection with the drill 50 (e.g., which may be according to thedescription above regarding measurement system 100). For example, atleast a portion of a displacement sensor 410 may be integrated into ahousing 26 of the drill 50. In this regard, the displacement sensor 410may include a depth sensing arm 412 that is specifically adapted forengagement with a bushing 452 of a drill bit assembly 60 that may beengaged by the chuck 420 of the drill 50.

In this regard, the depth sensing arm 412 may be used to establish areference point from which displacement of the drill bit 16 may bemeasured as described above. In this regard, as follows herein, ageneral description of the features and operation of the drill 50 usedin conjunction with the drill bit assembly 60 is provided.

As may be appreciated in FIGS. 10A-10C, the displacement sensor 410 mayinclude a depth sensing arm 412 that may extend from the drill housing26. For example, the depth sensing arm 412 may extend distally (e.g.,from a distal face 30 of the drill housing 26) in a directioncorresponding with the direction in which the drill bit 16 extends froma chuck 420 of the drill 50. At least a portion of the displacementsensing arm 412 may extend from the drill housing 26 parallel to an axisof rotation 120 of the drill 50. The depth sensing arm 412 may alsoinclude a distal portion 414 that is adapted to engage a bushing 452provided with the drill bit assembly 60 shown in FIG. 12. As usedherein, distal may correspond to a direction from the drill 50 towardthe leading edge 16 a of the drill bit 16 and proximal may correspond toa direction from the leading edge 16 a of the drill bit 16 toward thedrill 50. In this regard, at least a portion of the depth sensing arm412 (e.g., the distal portion 414) may be adapted to engage the bushing452 of the drill bit assembly 60 as will be described in more detailbelow. In any regard, at least a portion of the depth sensing arm 412may extend into the housing 26. With further reference to FIG. 11, thehousing 26 may contain a coil 416. As such, a proximal end 418 of thedisplacement sensing arm 412 may interface with the coil 416 of thedisplacement sensor 410 that may be disposed within the drill housing26.

Specifically, in FIG. 11, the depth sensing arm 412 is shown in aretracted position relative to the drill bit 16. As such, this retractedposition shown in FIG. 11 may occur when the drill bit 16 is advancedrelative to the bushing 452 during drilling (e.g., such that the portionof the drill bit extending beyond the distal edge of the bushing 452would be disposed in the medium to be drilled). In this regard, theproximal end 418 of the displacement sensing arm 412 is disposed withinthe coil 416 of the displacement sensor 410. Accordingly, thedisplacement sensor 410 may comprise an LVDT sensor as described abovethat is adapted to sense the position of a core 422 relative to a coil416. The displacement sensing arm 412 may incorporate a core 422 at theproximal end 418 thereof. Accordingly, as the proximal end 418 of thedisplacement sensing arm 412 is moved relative to the coil 416, thelocation of the core 422 may be determined to provide an outputcorresponding to the position of the core 422, and in turn thedisplacement sensing arm 412 relative to the drill housing 26. That is,the depth sensing arm 412 may be displaceable relative to the coil 416such that the displacement sensor 410 may be operable to sense a changein position of the depth sensing arm 412 relative to the drill housing26 and output a measure of the displacement that may be used asdescribed above in determining a depth of a bore. In an embodiment, thetotal measurable travel of the core 422 relative to the coil 416 may beat least about 2.5 in (6.4 cm). Furthermore, the resolution of theoutput of the displacement sensor 410 may be about 0.1% (e.g., about0.002 inches (0.06 mm) for a sensor having a total measureable travel of2.5 inches).

While a LVDT displacement sensor is shown and described in relation tothe drill 50 shown in the accompanying figures, it may be appreciatedthat other types of displacement sensors may be provided. For instance,the sensor may provide for the absolute or relative measurement of theposition of the distal end 418 of the displacement sensing arm 412 toprovide a displacement measure. For instance, in another embodiment, anoptical displacement sensor may be provided. Other types of displacementsensors are also contemplated such as, for example, a capacitivedisplacement sensor, ultrasonic sensors, Hall effect sensors, or anyother sensors known in the art capable of outputting an absolute orrelative position measure.

In an embodiment, the coil 416 may define a passage 424 extending atleast partially through the housing 26. Specifically, the passage 424may extend from a proximal face 32 of the housing 26 to the distal face30 of the housing 26. That is, the passage 424 may extend entirelythough the housing 26. An end cap 34 may be provided that is operable toclose the proximal end of the passage 424 at the proximal face 32 of thedrill housing 26. Furthermore, a biasing member 426 (e.g., a coilspring) may be provided in the passageway 424 at a proximal end thereof.The biasing member 426 may be provided between the end cap 34 and theproximal end 418 of the displacement sensing arm 412. In this regard,the biasing member 426 may act on the proximal end 418 of thedisplacement sensing arm 412 to bias the displacement sensing arm 412distally relative to the passage 424 and drill housing 26.

As such, the displacement sensing arm 412 may include features thatselectively prevent ejection of the displacement sensing arm 412 fromthe distal end of the passage 424. For example, the displacement sensingarm 412 may include at least one flat 428 that extends along a portionof the arm 412. At the proximal and distal extents of the flat 428, thedisplacement sensing arm 412 may include shoulders 436 that project fromthe flats 428 (best seen at the distal portion 414 in FIG. 10B and atthe proximal portion 418 in FIG. 11). As such, at the proximal openingof the passage 424, a selectively displaceable stop 438 (best seen inFIG. 23) may be disposed relative to the flat 428 such that the flat 428may move relative to the stop 438, but interfere with the shoulder 436defined in the displacement sensing arm 412 to prevent passage of theshoulder 436 beyond the stop 438. In this regard, the length of thedisplacement sensing arm 412 along which the flat 428 extends may bemoveable relative to the stop 438, and the stop 438 may limit proximaland distal movement of the displacement sensing arm 412 beyond the stop438.

However, the stop 438 may be displaceable upon depressing, for example,a button 440 provided on an exterior of the housing 26. Thus, upondepressing the button 440, the stop 438 may be displaced away from thedisplacement sensing arm 412 to allow the shoulder 436 to pass distallyfrom the distal end of the passage 424 such that the displacementsensing arm 412 may be removed entirely from the passage 424. The distalend of the flats 438 may include a detent 442 that may be engageablewith the stop 438 so as to maintain the displacement sensing arm 412 ina proximally disposed, retracted position relative to the housing (e.g.,as shown in FIG. 11). Once the button 440 is depressed and released, thedetent 442 at the proximal end of the flat 428 of the displacementsensing arm 412 may be released by the stop 438 and the displacementsensing arm 412 may move proximally (e.g., under influence of thebiasing member 426). The displacement sensing arm 412 may moveproximally until the shoulder 436 at the distal end of the flat 428 areengaged to prevent further distal movement of the displacement sensingarm 412. Accordingly, the displacement sensing arm 412 may be retainedin a retracted position (e.g., for improved visibility of the distal endof the drill bit 16), released to be moveable relative to and biasedproximally with respect to the housing 26, and removable altogether fromthe housing 26.

In the latter regard, removal of the displacement sensing arm 412 andbiasing member 426 from the passage 424 may allow for separate cleaning(e.g., in an autoclave) of those members. Additionally, removal of theend cap 34 may allow for a cleaning apparatus (e.g., a brush or thelike) to be passed through the full length of the passage 424 tofacilitate cleaning thereof.

As referenced above, the distal portion 414 of the displacement sensingarm 412 may be adapted to engage a drill bit assembly 60 (e.g., abushing 452 thereof) that is correspondingly adapted for use with thedrill 50. For instance, as shown in FIGS. 10A-10C and FIG. 11, thedisplacement sensing arm 412 may generally be linear along the proximalportion 418 of the displacement sensing arm 412. In this regard, theproximal portion 418 may be adapted to be collinear with the passage 424and moveable within the passage 424. Furthermore, the distal portion 414of the displacement sensing arm 412 (e.g., the portion distal to thelinear portion of the displacement sensing arm 412) may extend from thelinear portion of the displacement sensing arm 412 toward the drill bitassembly 60 that may be engaged by the chuck 420 of the drill 50. Inthis regard, the linear portion of the displacement sensing arm 412 maybe substantially parallel to and offset from the axis of rotation 120.The distal portion 414 may extend from the linear portion in a directioncorresponding with the offset such that the distal portion 414 extendstoward the drill bit assembly 60. This may facilitate engagement betweenthe displacement sensing arm 412 and the bushing 454 of the drill bitassembly 60. As shown, in FIGS. 10A-10C and 11, the distal portion 414may be an at least partially arcuate member extending along a radius ofcurvature toward the drill bit assembly 60. However, the distal portion414 may be shaped differently (e.g., the distal portion 414 may be alinear portion extending at an angle or perpendicularly from theproximal 418 toward the drill bit assembly 60).

With further reference to FIG. 12, an embodiment of a drill bit assembly60 that may be used in conjunction with the drill 50 is depicted. Thedrill bit assembly 60 may include a shank 454 that is disposed adjacentto a proximal end of the assembly 60. Furthermore, the assembly 60 maycomprise a leading edge 16 a at the distal end thereof. The leading edge456 may include a cutting edge that, when rotated serves to cut themedium into which the bit 16 is advanced as per a standard drill bit. Acylindrical member 458 (e.g., at least a portion thereof having flutesprovided therein to remove cut material from the cutting edge) mayextend between the shank 454 and the leading edge 456. The leading edge456, cylindrical body 458, and shank 454 may collectively define thedrill bit 16.

In addition to the drill bit 16, the drill bit assembly 60 may alsocomprise a bushing 452 as referenced above. The bushing 452 may engagethe cylindrical member 458 to facilitate relative movement of thebushing 452 relative to the cylindrical member 458 along a directioncorresponding to the axis of rotation 120. For example, the bushing 452may include an aperture 460 through which at least a portion of thecylindrical member 458 may be disposed. The aperture 460 may form acylindrical opening that extends at least in a direction correspondingto the axis of rotation 120 of the drill bit 16. The cylindrical openingmay be sized to receive the cylindrical member 458 therein such relativemovement between the cylindrical opening and the cylindrical member 458is provided. As such, the drill bit 16 may be free to rotate within theaperture 460, and the bushing 452 may slideably engage the cylindricalmember 458 for relative movement therebetween that is constrained alongthe direction corresponding to the axis of rotation 120.

The bushing 452 may include an engagement member 456 that is disposed onthe bushing 452 and adapted for engagement with a displacement sensingarm 412 of a drill 50 to which the drill bit assembly 60 is engaged. Forinstance, as depicted in FIG. 12, the engagement member 456 may comprisea post 462 extending from the bushing 452. The post 462 may extend awayfrom the axis of rotation 120 of the drill bit assembly 60. In anembodiment, the post 462 may extend perpendicularly to the axis ofrotation 120. Accordingly, the post 462 may engage a hole 464 providedon the distal portion 414 of the displacement sensing arm 412. In thisregard, the post 462 may extend into the hole 464. Movement of thebushing 452 relative to the drill bit 16 in a direction corresponding tothe axis of rotation 120 may result in the post 462 acting on the hole464 such that the displacement sensing arm 412 undergoes correspondingmovement upon movement of the bushing 452 relative to the drill bit 16.In turn, as described above, the core 422 at the proximal portion 418the displacement sensing arm 412 may also undergo corresponding movementrelative to the coil 416, which may be detected by the displacementsensor 410 and output as a displacement measure.

It may be appreciated that other arrangements for engaging the bushing452 with the displacement sensing arm 412 may be provided so that thebushing 452 and displacement sending arm 412 undergo correspondingmovement. For example, other structures such as clasps, fasteners, orother mechanisms may be utilized to engage the bushing 452 to thedisplacement sensing arm 412. Furthermore, the bushing 452 may, in someembodiments, be integrally defined on the distal portion 414 of thedisplacement sensing arm 412. In this regard, a standard drill bit 16may be engaged with a chuck 420 of the drill 50 and the bushing 452 maybe disposed relative to the bit 16. In any regard, the bushing 452 maybe pivotal relative to the displacement sensing arm 412 (e.g., in adirection perpendicular to the axis of rotation 120) to facilitate easeof engagement of the bushing 452 with the displacement sensing arm 412or the bushing 452 with the drill bit 16 when engaging the drill bit 16with the chuck 420 of the drill 50.

For example, with reference to FIGS. 20A-20D, a progression of imagesare shown that illustrate engagement of the drill bit assembly 60 with adrill 50. In FIG. 20A, the drill bit assembly 60 is grasped by a user atthe bushing 452. Thereafter in FIG. 20B, the post 462 of the bushing 452is disposed in a hole 464 of the displacement sensing arm 412 extendingfrom the drill housing 26. As may be appreciated, given the cylindricalinterface between the post 462 and the hole 464, the bushing 452 anddrill bit 16 may still be rotatable perpendicularly to the axis ofrotation 120. As such, the shank 454 may be aligned with the chuck 420as shown in FIG. 20C. Thereafter, the drill bit 16 may be movedproximally such that the chuck 420 engages the shank 454. As shown anddescribed in greater detail below, the chuck 420 may comprise a“quick-change” style chuck that allows for rapid insertion and removalof drill bits 16 therefrom. However, other types of chucks may beutilized without limitation such as, for example, a jawed chuck, acollet, a magnetic chuck, etc.

In any regard, the shank 454 of the drill bit assembly 60 may be engagedwith the chuck 420 of the drill 50. In this regard, the drill bit 16 maybe fixed relative to the drill 50 in the direction along the axis ofrotation 120. In turn, the bushing 452 may be displaceable relative tothe drill bit 16 along the axis of rotation 120. In this regard, whenthe drill bit 16 is advanced into a medium during a drilling operation,the bushing 452 may remain stationary at a reference point establishedprior to the drilling operation and the displacement sensor 410 may beoperable to detect the relative motion between the drill bit 16 and thebushing 452 retained in a stationary position relative to the referencepoint, thus providing a measure of the relative movement of the drillbit 16 relative to the reference point.

For instance, with further reference to FIG. 22, a schematic sectionview of a drill bit 16 that has been advanced into a medium 550 isshown. The bushing 452 may be disposed about the drill bit 16. As such,the bushing 452 may be disposed about the periphery of the bore 556created upon advancement of the drill bit 16 into the medium 550. Thatis, the bushing 452 may remain in contact with the surface 552 of themedium 550 upon advancement of the drill bit 16 into the medium 550. Inthis regard, the bushing 454 may include a reference surface 554 at adistal portion thereof. The reference surface 554 may contact thesurface 552 of the medium 550 to be drilled. As such, prior toinitiation of the drilling when the leading edge 16 a of the drill bit16 is also in contact with the surface 552, the displacement sensor 410may be set to establish the reference point. Accordingly, as the drillbit 16 is advanced, the reference surface 554 may remain in contact withthe surface 552 of the medium 550. The reference surface 554 may contactthe surface 552 about a periphery of the bore 556. In an embodiment, thereference surface 554 may extend circumferentially about a majority orsubstantially all of the drill bit 16 such that the reference surface554 may also extend circumferentially about a majority of orsubstantially all of the periphery of the bore 556. The distally biaseddisplacement sensing arm 412 may act on the bushing 452 (e.g., by way ofpost 462 received in hole 464) to maintain the bushing 452 in contactwith the surface 552. In any regard, the displacement (d) of the leadingedge 16 a of the drill bit 16 relative to the reference surface 554 ofthe bushing 454 may be measured upon corresponding movement of the core422 at the proximal end 418 of the displacement sensing arm 412 relativeto the coil 416.

In this regard, measurement of the displacement of the leading edge 16 aof the drill bit 16 relative to the reference surface 554 of the bushing454 that is maintained against the surface 552 of the medium 550 to bedrilled may provide improved accuracy regarding the displacement of theleading edge 16 a into the bore 556. As described above, as thereference surface 554 is maintained in contact with the medium 550adjacent to the periphery of the bore 556, there is less possibility forrelative movement between the bushing 452 and the medium 550 that mayintroduce error into the measured displacement d. Furthermore, as thebushing 452 is in contact with the medium 550 adjacent to the bore 556,the contact with the patient required to obtain the measurement islessened as the extension 110 may not need to contact the patient in alocation away from the bore 556. Thus, the drilling operation is lessinvasive, thus improving patient outcomes.

A number of additional features may also be provided for the drill 50and/or drill bit assembly 60 that are described in conjunction with theembodiment of the drill 50. It may be appreciated that these featuresmay be provided with other types of drills and/or drill bit assemblies60 and are not required to be used in conjunction with a drill 50 anddrill bit assembly 60 incorporating features for coordinated operationbetween the displacement sensor 410 and drill bit assembly 60 asdescribed above.

For instance, as may be further appreciated with reference to FIGS.13-15, a drill bit 16 may incorporate features that prevent reuse of thedrill bit 16. In this regard, surgical drill bits are often employed assingle use items such that the bits are specifically designed to be usedfor a single procedure or portion thereof and disposed after use ratherthan being reused. There are several rationales for doing so, includingthe safety of the patient to ensure that the drill bit 16 to be used ina procedure has not been worn or damaged by use in previous procedures.In this regard, the features described below may help prevent the drillbit 16 from being reused. As may be appreciated, the drill bit 16disclosed in this respect may be used in a drill bit assembly 60 asdescribed above.

Specifically, the drill bit 16 may include a destructible portion 466 ofthe shank 454. The destructible portion 466 may be degraded or destroyedwhen exposed to common cleaning procedures to which surgical instrumentsare routinely exposed. Upon destruction of the destructible portion 466,the shape of the shank 454 may be altered. The altered shape of theshank 454 may result in a reduced ability to engage the drill bit 16with a chuck 420. Such cleaning procedures may include exposure to steamcleaning at elevated heat and/or pressure in an autoclave process or mayinclude exposure to cleaning chemicals or the like. In this regard,when, for example, the destructible portion 466 is exposed totemperatures associated with cleaning in an autoclave, the destructibleportion 466 may be degraded or destroyed (e.g., by melting or otherdegradation due to heat) to prevent reuse of the drill bit assembly 60.Accordingly, in an embodiment, the melting temperature of thedestructible portion may be greater than an operating temperature (e.g.,substantially similar to room temperature or 22.3° C. +/−20° C.).Accordingly, in an embodiment, the melting temperature may be not lessthan about 50° C. and not greater than about 130° C. In an embodiment,the melting temperature of the destructible portion may be not less thanabout 60° C. and not greater than about 110° C.

While autoclave cleaning is a common method of sterilization andcleaning of instruments between procedures, it may be appreciated thatother methods of cleaning may be employed. As such, the destructibleportion 466 may be adapted to be degraded or destroyed during suchcleaning procedures. For example, the destructible portion 466 couldalternatively or additional be adapted to be degraded or destroyed uponexposure to a cleaning element such as a cleaning chemical or the like.In any regard, upon an attempt to sterilize or otherwise clean the drillbit assembly 60 for reuse, the destructible portion 466 may be destroyedor degraded to the point of eliminating the effectiveness of the drillbit assembly 60 to prevent reuse of the drill bit assembly 60.

With further reference to FIG. 13, one particular embodiment of a drillbit assembly 60 including a destructible portion 466 is shown where thedestructible portion may comprise a portion of the shank 454 of thedrill bit assembly 60. As shown, the destructible portion 466 comprisesa proximal end of the shank 454. As such, at least a portion of asidewall 468 and/or an endwall 470 of the shank may be defined by thedestructible portion 466. As may be appreciated with further referenceto FIGS. 15 and 16, the shank sidewall 468 and endwall 470 may beadapted for engagement with the chuck 420 such that the chuck 420contacts the sidewalls 468 and endwall 470 upon engagement with theshank 454.

For instance, as shown in FIG. 15, the chuck 454 may include acorrespondingly-shaped opening 472 that is sized to have correspondingsidewalls 474 that may contact the sidewalls 468 of the shank 454 whenthe shank 454 is received in the chuck opening 472. For instance, asshown, the sidewall 468 of the shank 454 may generally be arranged in asquare and the chuck sidewall 474 of the chuck opening 472 may becorrespondingly shaped and sized to accommodate the sidewalls 468. Assuch, upon receipt of the shank 454 in the chuck opening 472, the chucksidewalls 474 and shank sidewalls 468 may define a bearing surfaceinterface that allows the chuck 420 to impart rotational motion to thedrill bit 16. Furthermore, the chuck opening 472 may have a depth thatallows the endwall 470 of the shank 454 to register relative to thechuck opening 472 when the shank 454 is received in the chuck opening472.

Accordingly, when, as shown in FIG. 14, the destructible portion 466 isdestroyed or degraded, at least a portion of the sidewall 468 or endwall470 may be removed. The result may be at least a lack of registration ofthe shank 454 relative to the chuck opening 472. This may prohibit theability of the drill bit assembly 60 to be used because the lack ofregistration may prevent the drill bit 16 from properly turning so as toat least inhibit the use of the drill bit assembly 60 in a procedure.For instance, the bearing surface interface between the chuck sidewalls474 and the shank sidewall 468 may be degraded such that the chuck 420may not be capable of imparting rotational motion to the drill bit 16.Additionally or alternatively, the destructible portion 466 may bedegraded to the point where the shank 454 is no longer receivable by thechuck 420.

As may also be appreciated in FIGS. 13 and 14, the shank 454 may includechuck engagement features that may be engaged by the chuck 420 to retainthe drill bit assembly 60 relative to the chuck 420. For instance, thechuck 420 may include retention pins 476 that are biased to extend intothe chuck opening 472 from the chuck sidewall 474 in an engaged positionto engage detents 478 of the shank 454. For instance, a biasing member480 may bias a chuck collar 482 distally relative to the chuck opening472. The collar 482 may be engaged with the pins 476 to bias the pins476 into the engaged position. Upon movement of the collar 482proximally relative to the chuck opening 472, the pins 476 may be freedso as to allow movement away from the engaged position (e.g., to receivethe shank 454 or release the shank 454 during normal operation as iscommon with “quick-release” type chucks). Correspondingly, the detents478 of the shank 454 may be released and the shank 454 may be releasedfrom the chuck 454. In an embodiment, the destructible portion 466 mayinclude the detents 478 such that the shank 454 may not be retained bythe pins 476 once the destructible portion 466 is degraded or destroyed.

Furthermore, the drill 50 may include a removable chuck 420 thatprovides for quick interchange and/or removal of the chuck 420. As mayfurther be appreciated from FIG. 11, the drill 50 may include a drive430. The drive 430 may a motor 432 and gearbox 434. The drive 430 mayengage a chuck 420. Specifically, the chuck 420 may be provided inremovable engagement with the drive 430 such that the chuck 420 may bereleasably engaged with the drive 420. As may be further appreciated inFIG. 16, the chuck 454 may include a chuck drive coupling 484 at aproximal end thereof. In this regard, as may be appreciated in FIG. 17,the drill 50 may include a corresponding drill drive coupling 486 thatengages with the chuck drive coupling 484 to impart rotational motionfrom the drive 430 to the chuck 420. In this regard, the chuck 420 maybe detachable from the drill 50.

For instance, with further reference to FIG. 18, the proximal end of thechuck 420 may include slots 488 that may coordinate with correspondingtabs 490 (best seen in FIG. 19B) to retain the chuck 420 relative to thedrill 50 such that the dill drive coupling 486 engages the chuck drivecoupling 484 to impart rotational motion thereto. The slots 488 maycoordinate with the tabs 490 so to allow the chuck 420 to be quicklyattached and/or released from the drill 50 by engagement of the slots488 with the tabs 490. The tabs 490 may be operatively engaged with arelease 492. Accordingly, upon actuation of the release (e.g., from theexterior of the drill housing 26), the tabs 490 may disengage the chuck420 to allow the chuck to be removed. Thus, the chuck 420 may be quicklyand efficiently attached and detached from the drill 50.

With further reference to FIGS. 19A and 19B, cross sectional views ofthe drill 50 with drill bit assembly 60 engaged therewith are shown. Asmay be appreciated, the drill drive coupling 486 may engage the chuckdrive coupling 484. As may also be appreciated, the chuck 450 may beoperatively engaged with the drill drive 430 such that the engagement ofthe slots 488 of the chuck 420 are engaged with the tabs 490 disposedrelative to the drill body 26. As may also be appreciated in FIGS. 19Aand 19B, a destructible portion 466 of the shank 454 may be intact suchthat the sidewalls 468 the shank 454 are in registration withcorresponding sidewalls 470 of the chuck opening 472 and the endwall 470of the shank 454 is seated against the proximal end of the chuck opening472. Furthermore, the detents 478 in the shank 454 may coordinate withthe pins 476 that are biased relative to the detents 476 by way of theaction of the distally biased collar 482 thereon. In this regard, thedrill bit 16, chuck 420, and drill drive 430 may comprise a rigidassembly along a direction corresponding to the axis of rotation 120.Accordingly, as will be described in greater detail below, a forceacting on the leading edge 16 a of the drill bit 16 may in turn betransmitted throughout the rigid assembly.

With specific reference to FIG. 19A, it may be appreciated that thebushing 452 of the drill bit assembly 60 may be engaged with the distalportion 414 of the displacement sensing arm 412. Accordingly, as may beappreciated, the drill bit 16 may be operatively engaged with the chuck420 so as to limit relative movement therebetween along the axis ofrotation 120 such that relative movement between the bushing 452 anddisplacement sensing arm 412 may be sensed as described above.

As may be appreciated, when drilling using the drill 50, a second sensorfor measurement of force acting on the leading edge 16 a of the drillbit 16 may also be provided. In this regard, a second sensor 118′ (e.g.,a force sensor such as piezoelectric crystal) may be disposed proximallyto the drill drive 430. In turn, force acting on the leading edge 16 aof the drill bit 16 as it is advanced in the drilling process may betransferred to the second sensor 118′ via the drill drive 430. That is,the force acting on the leading edge 16 a of the drill bit 16 may betransferred through the shank 454 of the bit 16 to the chuck 420, andthe drill drive 420. In turn, the drive 430 may act upon the secondsensor 118′ to produce an output corresponding to the force acting onthe leading edge 16 a. In this regard, it may be appreciated that therigid assembly of the drill drive 430, chuck 420, and drill bit 16 maytransmit the force acting on the leading edge 16 a of the drill bit 16to the second sensor 118. It may further be appreciated that the drilldrive 430 may be fixed rotationally relative to the drill housing 26 soas to impart rotation to the chuck 420. However, the drill drive 430 ispreferably free to move in a direction along the axis of rotation 120such that the at least a majority of the force acting on the leadingedge 16 a of the drill bit 16 may be transferred to the second sensor118. In an embodiment, the second sensor 118 may have a range ofmeasureable force from about 0 lbf (0 N) to about 100 lbf (445 N). In anembodiment, the second sensor 118 may have a range of measurable forcefrom about 0 lbf (0 N) to about 25 lbf (111 N). The second sensor 118may have a precision of at least about 1% of the maximum measureableforce. Accordingly, in an embodiment, the second sensor may have aprecision of at least about 0.25 lbf (1.1 N). In an embodiment, thesecond sensor 118 may have a precision of 0.5% (e.g., about 0.125 lbf(0.56 N) in an embodiment).

In this regard, the drill drive 430, as shown best in FIGS. 11 and 19Amay be mounted to the drill housing 26 by way of a suspension member494. The suspension member 494 may be operatively engaged to the drillhousing 26 and the drill drive 430 so as to maintain the drill drive 430stationary with respect to rotation about to the axis of rotation 430,yet allow for at least some movement of the drill drive 430 axiallyrelative to the axis of rotation 120 to transfer force acting on theleading edge 16 a of the drill bit 16 to the second sensor 118. As such,the suspension member 494 may be supportively engaged to the drill drive430 at a first end of the suspension member 494. The suspension member494 may also be affixed to the drill housing 26. The suspension member494 may be relatively rigid relative to a direction corresponding torotation about the axis of rotation 120 so as to maintain the drilldrive 430 stationary with respect to rotation about the axis ofrotation. However, the suspension member 494 may allow for linearmovement along the axis of rotation 120. In this regard, the suspensionmember 494 may comprise a spring member that allows for motion relativeto the direction along the axis of rotation 120. The spring member mayhave a spring coefficient slight enough relative to the directioncorresponding to the axis of rotation 120 such that the force resultingfrom displacement of the suspension member 494 may be insignificant(e.g., less than about 1%, less than about 0.5% or even less than about0.1%) of the force applied to the leading edge 16 a of the drill bit 16during the drilling operation. It may be appreciated that the drilldrive 430 may additionally or alternatively mounted relative to thehousing 26 to facilitate movement in the direction along the axis ofrotation 120 while resisting rotational movement about the axis ofrotation 120. For instance, the drill drive 430 may incorporate a tab136 and slot 138 as described above relative to chuck 28 to facilitatelinear motion along the axis of rotation 120 while resisting rotationalmotion about the axis of rotation 120.

The drill may also include a light emitter 500 disposed on a distal face30 of the drill hosing 26. In this regard, the light emitter 500 may beoperable to emit light in a direction toward the drill bit 16 whenengaged with the chuck 420. As such, the light emitter 500 mayilluminate at least a portion of the drill bit 16 during the drillingoperation to improve visibility of the medium being drilled. The lightemitter 500 may comprise a light source such as, for example, anincandescent bulb, a light emitting diode (LED), a laser source, orother light source known in the art. Alternatively, a light source maybe disposed remotely from the light emitter 500 and the light may betransmitted from the remote light source to the light emitter 500 usingoptical elements such as fiber optics or the like. It may further beappreciated that a light emitter 500 like the one shown in theaccompanying figures may be provided with other types of surgicalinstruments without limitations. For example, a light emitter 500 of thetype described herein may be provided with other types of drills, saws,or other surgical tools. Accordingly, the light emitter 500 may beappropriately disposed relative to the surgical field so as to directlight from the light emitter 500 toward the interface of the surgicaltool with the portion of the surgical field contacted by the surgicaltool.

The light emitter 500 may be selectively operated or may be operatedwhen the drill 50 is operated. In this regard, the light emitter 500 maybe selectively toggle on and off or may include different levels ofintensity. The selector for the light emitter 500 may be at thecontroller housing 146 (e.g., a selectable option on the display 152).The light emitter 500 may also be activated upon activation of the drill50. Additionally, the operation of the light emitter 500 may beselectable between operation with the drill 500 and selective togglingof the light emitter 500.

In a further embodiment, the light emitter 500 may be adapted for usewith any appropriate surgical instrument. In this regard, furtherexamples of surgical instruments are shown in FIGS. 24A, 24B, and 24C,respectively. For example, in FIG. 24A, a burr grinder 600A is shown, inFIG. 24B, a sagittal saw 600B is shown with a first grip embodiment, andin FIG. 24C, a sagittal saw 600C is shown with a second grip embodiment.In FIG. 24A, the burr grinder 600A may include an instrument workingportion comprising a rotatable burr grinding bit 610. In this regard,the burr grinding bit 610 may be contactable with the patient to performa grinding operation. The burr grinder 600A may also include one or morelight emitters 500. As may be appreciated, the light emitters 500 may bedisposed on a distal face 620 of the burr grinder 600A such that thelight emitters 500 may be operable to emit light in a direction towardthe patient when the burr grinding bit 610 is in contact with thepatient. That is, the light emitter 500 may act to illuminate a surgicalfield in which the burr grinder 600A is employed. In the case of aplurality of light emitters 500, the light emitters may be spacedequally about a portion of the distal face 620 surrounding the workingportion of the burr grinder 600A. The light emitters 500 may be disposedwithin a housing of the burr grinder 600A such that the light emitters500 may be protected from environmental elements (e.g., fluid or thelike) that may be present when the burr grinder 600A is in use. As such,the light emitters 500 may include or be disposed behind a transparentor translucent shield 630 that may protect the light emitters 500 and/orlight source associated with the light emitters 500 from suchenvironmental elements. The light emitters 500 shown in FIG. 24A may beoperated according to any of the foregoing discussion regarding thelight emitters 500 described above.

Furthermore, with further reference to FIGS. 24B and 24C, it may beappreciated that the light emitters 500 may be provided in connectionwith other surgical instruments. For instance, in FIG. 24B, a sagittalsaw 600B with a first grip embodiment (i.e., a pistol grip style grip)is shown. In this regard, it may be appreciated that a sagittal sawblade 612 may be provided as the working portion of the sagittal saw600B. As such, the sagittal saw blade 612 may be reciprocated such thatcontact of the distal portion of the sagittal saw blade 612 may act tocut anatomy of the patient. As such, the light emitters 500 may bedisposed on a distal face of the sagittal saw 600B such that the lightemitters 500 may emit light toward the patient when the sagittal sawblade 612 contacts the patient in a cutting operation. Further still,FIG. 24C shows another embodiment of a sagittal saw 600C with a secondgrip embodiment. As may be appreciated, the light emitters 500 of thesagittal saw 600C may be disposed about the sagittal saw blade 612 in amanner as described above with respect to the burr grinder 600A.

Those skilled in the art will appreciate that changes could be made tothe embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1-46. (canceled)
 47. A drill including a drill bit penetration measuringsystem for determining, with respect to a reference point, a depth ofpenetration of a leading edge of a drill bit in a bore, the drillcomprising: a chuck for engagement with a shank of a drill bit, whereinthe chuck is operable to constrain a drill bit engaged by the chuck tolimit relative axial movement relative to an axis of rotation aboutwhich the drill bit is rotated during drilling; a displacement sensingarm extending from the drill, wherein the displacement sensing arm isengageable with a bushing member that is constrainedly moveable alongthe axis of rotation with respect to a drill bit engaged by the chuck;and a displacement sensor disposed in a fixed relative position withrespect to a drill bit engaged by the chuck at least in a directioncorresponding to the axis of rotation, the displacement sensing armbeing adapted for relative movement with respect to the displacementsensor, wherein the displacement sensor is operative to output a firstsignal representative of the displacement of the drill sensing armrelative to the displacement sensor; wherein the movement of thedisplacement sensing arm relative to the drill corresponds todisplacement of the bushing relative to a drill bit engaged by thechuck.
 48. The drill according to claim 47, wherein the displacementsensor is disposed internally to a drill housing and the displacementsensing arm extends from the drill housing.
 49. The drill according toclaim 48, wherein at least a portion of the displacement sensing armextends from the drill housing parallel to and offset from the axis ofrotation.
 50. The drill according to claim 49, wherein at least aportion the displacement sensing arm extends towards a drill bit engagedby the chuck.
 51. The drill according to claim 50, wherein thedisplacement sensing arm comprises a hole engageable with a post of thebushing to effectuate corresponding movement of the displacement sensingarm and the bushing.
 52. The drill according to claim 50, wherein thedisplacement sensor comprises a linear variable differentialdisplacement transducer (LVDT), wherein a coil of the LVDT is disposedin the housing and the displacement sensing arm comprises a moveablecore displaceable with respect to the coil of the LVDT.
 53. The drillaccording to claim 52, wherein the displacement sensor comprises a totalmeasureable travel of at least about 6.4 cm.
 54. The drill according toclaim 53, wherein the drill has a resolution of at least about 0.06 mm.55. The drill according to claim 52, wherein the displacement sensingarm is biased to a distal position relative to a drill bit engaged bythe chuck.
 56. The drill according to claim 55, wherein the displacementsensing arm is selectively removable from the drill housing.
 57. Thedrill according to claim 56, wherein the displacement sensing arm isselectively removable from a passage extending through the drillhousing, wherein the passageway is selectively opened from a proximalend thereof to a distal end thereof.
 58. The drill according to claim56, wherein the displacement sensing arm is selectively retainable in aproximal position.
 59. The drill according to claim 47, wherein thechuck comprises a removable assembly engaged to a drive motor by way ofa coupling receiver, wherein the removable assembly is attached to thedrill by way of a release mechanism.
 60. The drill according to claim47, further comprising: a light emitter operable to emit light in adirection toward the drill bit retained by the chuck.
 61. A method foruse of a drill including a drill bit penetration measuring system fordetermining, with respect to a reference point, a depth of penetrationof leading edge of a drill bit in a bore, comprising: engaging a shankof a drill bit with a chuck of the drill; constraining the drill bitengaged by the chuck to limit axial movement relative to an axis ofrotation about which the drill bit is rotated during drilling; andconnecting a displacement sensing arm extending from the drill to abushing member that is constrainedly moveable along the axis of rotationwith respect to the drill bit engaged with the chuck.
 62. The methodaccording to claim 61, further comprising: aligning a distal edge of thebushing with a leading edge of the drill bit; moving the displacementsensing arm relative to a displacement sensor of the drill; andestablishing the reference point upon alignment of the distal edge ofthe bushing with the leading edge of the drill bit.
 63. The methodaccording to claim 62, further comprising: rotating the drill bit torotatably advance the drill bit in a bore; and detecting a relativemovement of the drill bit relative to the reference point by way ofcorresponding movement of the displacement sensing arm relative to thedisplacement sensor.
 64. The method according to claim 63, furthercomprising: biasing the displacement sensing arm to a distal position,wherein the biasing maintains the distal edge of the bushing in contactwith a medium into which the drill bit is rotationally advanced. 65-82.(canceled)